Vehicle Air Compressor Apparatus for a Heavy Vehicle Air Braking System

ABSTRACT

A vehicle air compressor apparatus is provided for a heavy vehicle air braking system. The apparatus comprises a crankcase, and a cylinder head disposed on the crankcase. The cylinder head includes (i) an air inlet port through which air can be received for compression within the crankcase and the cylinder head, (ii) a discharge port through which compressed air can be delivered from the cylinder head, (iii) a first port through which compressed air can pass, and (iv) a second port through which cooled compressed air can pass. The apparatus further comprises a discharge air cooling jumper connected externally of the cylinder head between the first and second ports. The jumper is arranged to cool compressed air passing from the first port through a discharge air path of the jumper to the second port to provide cooler compressed air to be delivered from the cylinder head through the discharge port.

BACKGROUND

The present application relates to heavy vehicle braking systems, and isparticularly directed to a vehicle air compressor apparatus for a heavyvehicle air braking system, such as a truck air braking system.

A truck air braking system includes a vehicle air compressor whichbuilds air pressure for the air braking system. The compressor istypically cooled by an engine coolant system and lubricated by an engineoil supply. A governor controls system air pressure between a presetmaximum and minimum pressure level by monitoring the air pressure in asupply reservoir. When the supply reservoir air pressure becomes greaterthan that of a preset “cut-out” setting of the governor, the governorcontrols the compressor to stop the compressor from building air andalso causes an air dryer downstream from the compressor to go into purgemode. As the supply reservoir air pressure drops to a preset “cut-in”setting of the governor, the governor returns the compressor back tobuilding air and the air dryer to air drying mode.

Air discharged from the compressor gains a significant amount of heatduring the compression process. A discharge line interconnects thecompressor and the air dryer to deliver compressed air from thecompressor to the downstream air dryer. The compressed air cools as theair moves from the compressor through the discharge line to the airdryer. A larger diameter discharge line helps to cool the compressed airmore as the air moves from the compressor to the air dryer. Also, alonger length discharge line helps to cool the compressed air more asthe air moves from the compressor to the air dryer. It would bedesirable to provide a vehicle air compressor apparatus which provideseven more cooling of air discharged from the compressor.

SUMMARY

In accordance with one embodiment, a vehicle air compressor apparatus isprovided for a heavy vehicle air braking system. The vehicle aircompressor apparatus comprises a compressor crankcase assembly, and acompressor cylinder head assembly disposed on the crankcase assembly.The cylinder head assembly includes (i) an air inlet port through whichair can be received for compression within the crankcase and cylinderhead assemblies, (ii) a discharge port through which compressed air canbe delivered from the cylinder head assembly, (iii) a first intermediateport through which compressed air can pass, and (iv) a secondintermediate port through which cooled compressed air can pass. Thevehicle air compressor apparatus further comprises a discharge aircooling jumper connected externally of the cylinder head assemblybetween the first and second intermediate ports. The discharge aircooling jumper is arranged to cool compressed air passing from the firstintermediate port through a discharge air path of the jumper to thesecond intermediate port and thereby to provide cooler compressed air tobe delivered from the cylinder head assembly through the discharge port.

In accordance with another embodiment, a vehicle air compressorapparatus is provided for a heavy vehicle braking system. The vehicleair compressor apparatus comprises a compressor crankcase assembly, anda compressor cylinder head assembly disposed on the crankcase assembly.The cylinder head assembly co-operates with the crankcase assembly togenerate compressed air. The cylinder head assembly includes (i) an airinlet port through which air can be received for compression within thecrankcase and cylinder head assemblies, and (ii) a discharge portthrough which compressed air can be delivered from the cylinder headassembly. The vehicle air compressor apparatus further comprises coolingmeans connected externally of the crankcase and cylinder headassemblies. The cooling means is provided for cooling compressed airbefore the compressed air is delivered from the cylinder head assemblythrough the discharge port to deliver cooler compressed air through thedischarge port.

In accordance with yet another embodiment, a vehicle air compressorapparatus for a heavy vehicle braking system. The vehicle air compressorapparatus comprises a compressor cylinder head assembly connectable to acrankcase assembly. The cylinder head assembly includes (i) an air inletport through which air can be received for compression within thecrankcase and cylinder head assemblies, (ii) a discharge port throughwhich compressed air can be delivered from the cylinder head assembly,(iii) a first intermediate port through which compressed air can pass,and (iv) a second intermediate port through which cooled compressed aircan pass. The vehicle air compressor apparatus further comprises adischarge air cooling jumper connected externally of the cylinder headassembly between the first and second intermediate ports. The dischargeair cooling jumper is arranged to cool compressed air passing from thefirst intermediate port through a discharge air path of the jumper tothe second intermediate port and thereby to provide cooler compressedair to be delivered from the cylinder head assembly through thedischarge port.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicle air brake charging systemincluding a vehicle air compressor apparatus constructed in accordancewith an embodiment.

FIG. 2A is a perspective view of a known vehicle air compressor for usein a heavy vehicle air braking system.

FIG. 2B is a top view, looking approximately in the direction of arrow“2B” shown in FIG. 2A, of the known vehicle air compressor of FIG. 2A.

FIG. 3A is a perspective view of the vehicle air compressor apparatusshown in FIG. 1.

FIG. 3B is a top view, looking approximately in the direction of arrow“3B” shown in FIG. 3A, and showing certain parts removed.

FIG. 3C is another perspective view, looking approximately in thedirection of arrow “3C” shown in FIG. 3A, of the vehicle air compressorapparatus of FIG. 3A.

FIG. 3D is a side view, looking approximately in the direction of arrow“3D” shown in FIG. 3A, of the vehicle air compressor apparatus of FIG.3A.

FIG. 4A is a top perspective view of a discharge air cooling jumpershown in the vehicle air compressor apparatus of FIG. 3A.

FIG. 4B is a bottom perspective view, looking approximately in thedirection of arrow “4B” shown in FIG. 4A, of the discharge air coolingjumper of FIG. 4A.

FIG. 4C is a sectional view, taken approximately along line 4C-4C shownin FIG. 4A, and showing a discharge air path in the discharge aircooling jumper.

FIGS. 5A and 5B are views similar to FIGS. 4A and 4B, respectively, andshowing another embodiment.

FIGS. 6A and 6B are views similar to FIGS. 4A and 4B, respectively, andshowing another embodiment.

FIGS. 7A and 7B are views similar to FIGS. 4A and 4B, respectively, andshowing another embodiment.

FIGS. 8A and 8B are views similar to FIGS. 4A and 4B, respectively, andshowing another embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, apparatus 100 is provided for use in an air brakecharging system of a heavy vehicle such as a truck. Apparatus 100 isconstructed in accordance with one embodiment.

Air compressor 102 includes compressor cylinder head assembly 104disposed on compressor crankcase assembly 106. Components of crankcaseassembly 106 and components of cylinder head assembly 104 co-operatetogether to generate compressed air.

Compressor 102 further includes discharge air cooling jumper 400 whichis disposed on cylinder head assembly 104. Structure and operation ofdischarge air cooling jumper 400 will be described later.

First discharge line 109 is pneumatically connected between cylinderhead assembly 104 and air dryer 108. Second discharge line 110 ispneumatically connected between air dryer 108 and supply reservoir 112.Air supply line 114 is pneumatically connected between supply reservoir112 and air braking system and air accessories (not shown) of thevehicle.

Governor 120 controls system air pressure between a preset maximum andminimum pressure level by monitoring the air pressure in pneumaticcontrol line 122 from supply reservoir 112. When air pressure in supplyreservoir 112 becomes greater than that of a preset “cut-out” setting ofgovernor 120, the governor controls compressor 102 on pneumatic controlline 124 to stop compressor from building air. Governor 120 alsocontrols purge valve 126 on pneumatic control line 128 to purge air fromair dryer 108. When air pressure in supply reservoir 112 drops to apreset “cut-in” setting of governor 120, the governor returns compressor102 back to building air and air dryer 108 to air drying mode.

Compressor 102 may be based on design of known “standard” Bendix BA-921®Compressor commercially available from Bendix Commercial Vehicle SystemsLLC located in Elyria, Ohio. The known BA-921® compressor is shown inFIGS. 2A and 2B, and is designated with reference numeral “202”in FIGS.2A and 2B. FIG. 2B is a top view, looking approximately in the directionof arrow “2B” shown in FIG. 2A.

Compressor 202 includes compressor cylinder head assembly 204 disposedon compressor crankcase assembly 206 in known manner. Cylinder headassembly 204 includes air inlet port 207 through which air can bereceived for compression within the crankcase assembly 206 and cylinderhead assembly 204. Cylinder head assembly 204 includes discharge port208 through which compressed air can be delivered from the cylinder headassembly 204. A pair of coolant ports 210, 212 is provided through whichcoolant can flow to cool cylinder head assembly 204 as compressed air isbeing generated. Cylinder head assembly 204 further includes safetyvalve port 214, and governor port 216 which is connectable through apneumatic control line to a governor. Known compressor 202 shown inFIGS. 2A and 2B can be modified to provide a vehicle air compressorapparatus 100, such as shown in FIG. 1.

Referring to FIGS. 3A, 3B, 3C, and 3D, compressor 102 of FIG. 1 isillustrated in detail. FIG. 3A is a perspective view of compressor 102shown in FIG. 1. FIG. 3B is a top view, looking approximately in thedirection of arrow “3B” shown in FIG. 3A, and showing certain partsremoved so that parts of cylinder head assembly 104 (FIG. 1) can beseen. FIG. 3C is a perspective view, looking approximately in thedirection of arrow “3C” shown in FIG. 3A. FIG. 3D is a side view,looking approximately in the direction of arrow “3D” shown in FIG. 3A.As already mentioned above, compressor 102 includes cylinder headassembly 104 disposed on crankcase assembly 106.

While compressor 102 including cylinder head assembly 104 and crankcase106, as shown in FIGS. 3A, 3B, 3C, and 3D, can be manufactured as a newcompressor, it is conceivable that the known BA-921 compressor shown inFIGS. 2A and 2B may be modified (i.e., retrofitted) to provide thestructure and operation of compressor 102 shown in FIGS. 3A, 3B, 3C, and3D. Such a modification is briefly described in the next couple ofparagraphs hereinbelow.

During modification of known compressor 202 of FIGS. 2A and 2B, “legacy”cylinder head assembly 204 is removed from “legacy” crankcase assembly206 and replaced with cylinder head assembly 104 of FIGS. 3A 3B, 3C, and3D. After cylinder head assembly 104 is connected to legacy crankcaseassembly 206, discharge air cooling jumper 400 is connected to cylinderhead assembly 104. It is also conceivable that discharge air coolingjumper 400 may be first connected to cylinder head assembly 104, andthen the combined unit of the cylinder head assembly 104 and thedischarge air cooling jumper 400 be connected to legacy crankcaseassembly 206.

It should be apparent that crankcase assembly 106 shown in FIG. 1 hasthe same structure as legacy crankcase assembly 206 shown in FIG. 2A. Itshould also be apparent that cylinder head assembly 104 shown in FIGS.3A, 3B, 3C, and 3D has a structure which is different from the structureof legacy cylinder head assembly 204 shown in FIGS. 2A and 2B.Accordingly, compressor 102 (shown in FIGS. 3A, 3B, 3C, and 3D) may beprovided by taking legacy compressor 202 (shown in FIGS. 2A and 2B) andreplacing legacy cylinder head assembly 204 with “new” cylinder headassembly 104 and discharge air cooling jumper 400 to provide “new”compressor 102.

Referring again to FIGS. 3A, 3B, 3C, and 3D, cylinder head assembly 104includes air inlet port 307 through which air can be received forcompression within crankcase assembly 106 and cylinder head assembly104. Cylinder head assembly 104 also includes discharge port 308 (FIG.3C) through which compressed air can be delivered from the cylinder headassembly 104. A pair of coolant ports 310, 312 is provided through whichcoolant can flow to cool cylinder head assembly 104 as compressed air isbeing generated. Cylinder head assembly 104 further includes governorport 316 (FIG. 3C) which is connectable through pneumatic control line124 (FIG. 1) to governor 120.

As shown only in FIG. 3B, cylinder head assembly 104 further includesfirst intermediate port 342 through which compressed air can pass, andsecond intermediate port 352 through which compressed air can pass.First intermediate port 342 is connectable in fluid communication to airinlet port 307 through a number of air passages which are internal tocylinder head assembly 104. Second intermediate port 352 is connectablein fluid communication to discharge port 308 through a number of airpassages which are internal to cylinder head assembly 104.

First cylinder head bearing surface 344 is located in the vicinity offirst intermediate port 342, and first O-ring 348 is on first cylinderhead bearing surface 344. Threaded bolt bores 346 are disposed onopposite sides of first intermediate port 342. Similarly, secondcylinder head bearing surface 354 is located in the vicinity of secondintermediate port 352, and second O-ring 358 is on second cylinder headbearing surface 354. Threaded bolt bores 356 are disposed on oppositesides of second intermediate port 352.

Referring to FIGS. 4A, 4B, and 4C, discharge air cooling jumper 400 isillustrated. FIG. 4B is a bottom perspective view, looking approximatelyin the direction of arrow “4B” shown in FIG. 4A. FIG. 4C is a sectionalview, taken approximately along line 4C-4C shown in FIG. 4A, and showingdischarge air path 462 in discharge air cooling jumper 400. Dischargeair cooling jumper 400 is connectable between first and secondintermediate ports 342, 352 of cylinder head assembly 104 to coolcompressed air passing therethrough, as will be described in detailherein. Discharge air cooling jumper 400 may comprise metal materialwhich is the same or similar to material of cylinder head assembly 104.For example, material of discharge air cooling jumper 400 may comprisealuminum. Material of discharge air cooling jumper 400 may comprisematerial other than metal material.

Discharge air cooling jumper 400 includes first end portion 440, secondend portion 450, and central portion 460 interconnecting first andsecond end portions 440, 450. First end portion 440 includes first port442 located at one end of discharge air path 462. Second end portion 450includes second port 452 located at opposite end of discharge air path462. Accordingly, discharge air path 462 extends between first andsecond end ports 442, 452 to define a substantially U-shaped air paththrough jumper 400.

Safety valve 470 is disposed at first end portion 440 of jumper 400.Machining hole plug 472 is disposed at second end portion 450 of jumper400.

First jumper bearing surface 444 is disposed at first end portion 440 ofjumper 400, and is located in vicinity of first port 442. Bolt holes 446are disposed on opposite sides of first port 442. Similarly, secondjumper bearing surface 454 is disposed at second end portion 450, and islocated in vicinity of second port 452. Bolt holes 456 are disposed onopposite sides of second port 452.

Discharge air cooling jumper 400 shown in FIGS. 4A, 4B, and 4C isconnected to cylinder head assembly 104 using bolts 401 (FIGS. 3A and3C). Bolts 401 pass through bolt holes 446, 456 of jumper 400, and arescrewed into threaded bores 346, 356 (FIG. 3B) in cylinder head assembly104. O-ring 348 is sandwiched between first cylinder head bearingsurface 344 and first jumper bearing surface 444 to provide an airtightseal therebetween. Similarly, O-ring 358 is sandwiched between secondcylinder head bearing surface 354 and second jumper bearing surface 454to provide an airtight seal therebetween. Also, when jumper 400 isconnected to cylinder head assembly 104, an air gap 320 (best shown inFIG. 3D) is defined between central portion 460 of jumper 400 andcylinder head assembly 104. Thus, central portion 460 of jumper 400 isspaced apart from cylinder head assembly 104.

The position of jumper 400 is located outside of cylinder head assembly104, and is exposed to ambient air. As such, jumper 400 experiencestemperatures less than temperatures experienced by cylinder headassembly 104. The result is that compressed air passing through jumper400 is cooled.

It should be apparent that head-cooled discharge air exits cylinder headassembly 104 and enters into discharge air path 462 of discharge aircooling jumper 400. Since jumper 400 is located outside of cylinder headassembly 104 and is exposed to ambient air, the discharge air is cooledbefore it enters back into cylinder head assembly 104 to be delivered todischarge port 308 (FIG. 3C).

It should further be apparent that a new compressor can be manufactured,or a legacy compressor can be modified to provide the additional coolingof air discharged from the compressor as described hereinabove.

It should also be apparent that port locations of a cylinder headassembly of a commercially available vehicle air compressor (i.e., thestandard Bendix BA-921® Compressor in the above-described example) havebeen modified without affecting the pneumatic function of thecompressor. More specifically, port locations of the BA-9210) have beenaltered to facilitate installation of discharge air cooling jumper 400to provide extra cooling of air discharged from the compressor. This isachieved without having to modify the compressor crankcase assembly.

A number of advantages result by providing either a newly-manufacturedcompressor or a modified commercially available vehicle air compressorin accordance with the above-described description. One advantage isthat the overall temperature of air discharged from the discharge portof the compressor is reduced. Engineering tests have indicated a 15% to50% reduction in the temperature of the air at the discharge port whencomparing a standard BA-921® compressor without a discharge air coolingjumper to the new compressor with the discharge air cooling jumper. Thistemperature reduction decreases the potential of carbon buildup at thedischarge port.

Another advantage is that compressed air is supplied at a more idealtemperature to downstream components. The result is improved operationof downstream components.

Although the above-description describes discharge air cooling jumper400 having a shape and configuration such as shown in FIGS. 3A, 3B, 3C,and 3D, it is conceivable that discharge air cooling jumper may have ashape and configuration involving any combination of a set of fittingsand a pipe, tubing, metal couplings, and the like.

Although the above-description describes a BA-921® compressor beingmodified to provide additional cooling of discharge air from thecompressor, it is conceivable that other commercially available vehicleair compressors may be modified to accomplish the same. It is alsoconceivable that commercially available vehicle air compressors may bemodified or new vehicle air compressors be designed to comprise morethan one discharge air cooling jumper.

Further, although the above-description describes apparatus 100 beingused in a heavy vehicle such as a truck, it is conceivable thatapparatus 100 may be used in other types of heavy vehicles, such asbusses for example.

Another embodiment is illustrated in FIGS. 5A and 5B. Discharge aircooling jumper 500 shown in FIGS. 5A and 5B has similar construction asdischarge air cooling jumper 400 shown in FIGS. 4A and 4B. Jumper 500further includes cooling fin or rib 580 disposed longitudinally on oneside of central portion 560 of jumper 500. Cooling fin 580 provides moresurface area exposed to ambient air to improve cooling effectiveness ofjumper 500.

Another embodiment is illustrated in FIGS. 6A and 6B. Discharge aircooling jumper 600 shown in FIGS. 6A and 6B has similar construction asdischarge air cooling jumper 400 shown in FIGS. 4A and 4B. Jumper 600further includes cooling fin or rib 680 disposed longitudinally on oneside of central portion 660 of jumper 600 and another cooling fin 682disposed longitudinally on opposite side of central portion 660 ofjumper 600. Cooling fins 680, 682 provide more surface area exposed toambient air to improve cooling effectiveness of jumper 600.

Another embodiment is illustrated in FIGS. 7A and 7B. Discharge aircooling jumper 700 shown in FIGS. 7A and 7B has similar construction asdischarge air cooling jumper 400 shown in FIGS. 4A and 4B. Jumper 700further includes at least one cooling fin 784 disposed longitudinally ontop side of central portion 760 of jumper 700. Jumper 700 also includesat least one cooling fin 786 disposed longitudinally on bottom side ofcentral portion 760 of jumper 700. Cooling fins 784, 786 provide moresurface area exposed to ambient air to improve cooling effectiveness ofjumper 700.

It is conceivable that any number of cooling fins be disposed on topside of central portion 760, and that any number of cooling fins bedisposed on bottom side of central portion 760. It is also conceivablethat only cooling fins are disposed on top side without any cooling finsdisposed on bottom side, or only cooling fins are disposed on bottomside without any cooling fins disposed on top side.

Another embodiment is illustrated in FIGS. 8A and 8B. Discharge aircooling jumper 800 shown in FIGS. 8A and 8B has similar construction asdischarge air cooling jumper 400 shown in FIGS. 4A and 4B. Jumper 800further includes at least one cooling fin or rib 888 disposed radiallyon central portion 860 of jumper 800. Radial cooling fin 888 providesmore surface area exposed to ambient air to improve coolingeffectiveness of jumper 800.

It should be apparent that above-described cooling fins or ribs changethe geometry of the jumper to improve cooling effectiveness of thejumper and thereby to provide extra cooling of compressed air travelingthrough the jumper. The number of cooling fins may be any combination ofside fins, top fins, bottom fins, or radial fins.

While the present invention has been illustrated by the description ofexample processes and system components, and while the various processesand components have been described in detail, applicant does not intendto restrict or in any way limit the scope of the appended claims to suchdetail. Additional modifications will also readily appear to thoseskilled in the art. The invention in its broadest aspects is thereforenot limited to the specific details, implementations, or illustrativeexamples shown and described. Accordingly, departures may be made fromsuch details without departing from the spirit or scope of applicant'sgeneral inventive concept.

What is claimed is:
 1. A vehicle air compressor apparatus for a heavyvehicle air braking system, the vehicle air compressor apparatuscomprising: a compressor crankcase assembly; a compressor cylinder headassembly disposed on the crankcase assembly and including (i) an airinlet port through which air can be received for compression within thecrankcase and cylinder head assemblies, (ii) a discharge port throughwhich compressed air can be delivered from the cylinder head assembly,(iii) a first intermediate port through which compressed air can pass,and (iv) a second intermediate port through which cooled compressed aircan pass; and a discharge air cooling jumper connected externally of thecylinder head assembly between the first and second intermediate portsand arranged to cool compressed air passing from the first intermediateport through a discharge air path of the jumper to the secondintermediate port and thereby to provide cooler compressed air to bedelivered from the cylinder head assembly through the discharge port. 2.A vehicle air compressor apparatus according to claim 1, wherein thedischarge air cooling jumper includes at least onelongitudinally-extending cooling fin disposed externally on a first sideof the jumper.
 3. A vehicle air compressor apparatus according to claim2, wherein the discharge air cooling jumper includes at least onelongitudinally-extending cooling fin disposed externally on a secondside of the jumper opposite the first side of the jumper.
 4. A vehicleair compressor apparatus according to claim 1, wherein the discharge aircooling jumper includes at least one longitudinally-extending coolingfin disposed externally on top of the jumper.
 5. A vehicle aircompressor apparatus according to claim 1, wherein the discharge aircooling jumper includes at least one longitudinally-extending coolingfin disposed externally on bottom of the jumper.
 6. A vehicle aircompressor apparatus according to claim 1, wherein the discharge aircooling jumper includes (i) at least one longitudinally-extendingcooling fin disposed externally on top side of the jumper, and (ii) atleast one longitudinally-extending cooling fin disposed externally onbottom of the jumper.
 7. A vehicle air compressor apparatus according toclaim 1, wherein the discharge air cooling jumper includes at least oneradially-extending cooling fin disposed externally around at least aportion of the jumper.
 8. A vehicle air compressor apparatus accordingto claim 1, wherein (i) the discharge air cooling jumper includes afirst end portion defining a first end of the discharge air path and asecond end portion defining second end of the discharge air path, and(ii) the discharge air path extends in a substantial U-shape between thefirst and second ends of the discharge air path.
 9. A vehicle aircompressor apparatus according to claim 8, wherein the discharge aircooling jumper includes a safety valve disposed at one of the first andsecond end portions of the jumper and connected in fluid communicationwith the discharge air path.
 10. A vehicle air compressor apparatusaccording to claim 8, wherein (i) the first end portion of the jumperdefines a first jumper bearing surface which faces a first cylinder headbearing surface in the vicinity of the first intermediate port of thecylinder head assembly, and (ii) the second end portion of the jumperdefines a second jumper bearing surface which faces a second cylinderhead bearing surface in the vicinity of the second intermediate port ofthe cylinder head assembly.
 11. A vehicle air compressor apparatusaccording to claim 10, wherein the cylinder head assembly includes (i) afirst O-ring disposed between the first jumper bearing surface and thefirst cylinder head bearing surface in the vicinity of the firstintermediate port to provide an air-tight seal between the bearingsurfaces, and (ii) a second O-ring disposed between the second jumperbearing surface and the second cylinder head bearing surface in thevicinity of the second intermediate port to provide an airtight sealbetween the bearing surfaces.
 12. A vehicle air compressor apparatusaccording to claim 1, wherein (i) the first intermediate port isconnectable in fluid communication to the air inlet port through a firstnumber of air passages which are internal to the cylinder head, and (ii)the second intermediate port is connectable in fluid communication tothe discharge port through a second number of air passages which areinternal to the cylinder head assembly.
 13. A vehicle air compressorapparatus for a heavy vehicle braking system, the vehicle air compressorapparatus comprising: a compressor crankcase assembly; a compressorcylinder head assembly disposed on the crankcase assembly andco-operating with the crankcase assembly to generate compressed air,wherein the cylinder head assembly includes (i) an air inlet portthrough which air can be received for compression within the crankcaseand cylinder head assemblies, and (ii) a discharge port through whichcompressed air can be delivered from the cylinder head assembly; andcooling means connected externally of the crankcase and cylinder headassemblies and for cooling compressed air before the compressed air isdelivered from the cylinder head assembly through the discharge port todeliver cooler compressed air through the discharge port.
 14. A vehicleair compressor apparatus according to claim 13, wherein the coolingmeans includes a discharge air cooling jumper including at least aportion spaced apart from the cylinder head assembly to cool compressedair while the compressed air is outside of the cylinder head assemblyand thereby to provide cooler compressed air to be delivered from thecylinder head assembly through the discharge port.
 15. A vehicle aircompressor apparatus according to claim 14, wherein the discharge aircooling jumper includes at least one cooling fin disposed externally onthe jumper.
 16. A vehicle air compressor apparatus according to claim15, wherein the at least one cooling fin comprises at least oneradially-extending cooling fin disposed externally on the jumper.
 17. Avehicle air compressor apparatus according to claim 15, wherein thedischarge air cooling jumper defines a substantially U-shaped dischargeair path within the jumper.
 18. A vehicle air compressor apparatusaccording to claim 17, wherein the discharge air cooling jumper includesa safety valve connected in fluid communication with the substantiallyU-shaped discharge air path within the jumper.
 19. A vehicle aircompressor apparatus for a heavy vehicle braking system, the vehicle aircompressor apparatus comprising: a compressor cylinder head assemblyconnectable to a crankcase assembly and including (i) an air inlet portthrough which air can be received for compression within the crankcaseand cylinder head assemblies, (ii) a discharge port through whichcompressed air can be delivered from the cylinder head assembly, (iii) afirst intermediate port through which compressed air can pass, and (iv)a second intermediate port through which cooled compressed air can pass;and a discharge air cooling jumper connected externally of the cylinderhead assembly between the first and second intermediate ports andarranged to cool compressed air passing from the first intermediate portthrough a discharge air path of the jumper to the second intermediateport and thereby to provide cooler compressed air to be delivered fromthe cylinder head assembly through the discharge port.
 20. A method ofretrofitting a vehicle air compressor apparatus of claim 19 to a vehicleair compressor having a legacy crankcase assembly and a legacy cylinderhead assembly disposed on the legacy crankcase assembly, wherein themethod comprises (i) removing the legacy cylinder head assembly from thelegacy crankcase assembly, (ii) connecting the compressor cylinder headassembly to the legacy crankcase assembly, and (iii) connecting thedischarge air cooling jumper to the compressor cylinder head assembly.21. A vehicle air compressor apparatus according to claim 19, whereinthe discharge air cooling jumper comprises at least one cooling findisposed externally on the jumper.
 22. A vehicle air compressorapparatus according to claim 19, wherein the discharge air coolingjumper defines a substantially U-shaped discharge air path within thejumper.
 23. A vehicle air compressor apparatus according to claim 22,wherein the discharge air cooling jumper includes a safety valveconnected in fluid communication with the substantially U-shapeddischarge air path within the jumper.